(a) Field of the Invention
The present invention relates to a film-type supercapacitor and a manufacturing method thereof, including a method for manufacturing an electrode film by using graphene or graphene oxide, a method for forming a two-dimensional electrode by separating graphene or a graphene oxide electrode film into two electrodes through a patterning method, an in-plane structure of the two-dimensional electrode, a method for forming a current collector on a electrode, and a method for manufacturing a supercapacitor with a micrometer thickness by supplying an electrolyte to the two-dimensional electrode.
(b) Description of the Related Art
Portable electronic devices that have been down-sized have gradually developed into very small models, and batteries have been built into the portable electronic devices so as to maximize the performance in consideration of the devices becoming thinner. The portable electronic devices will eventually progress to devices that are very thin like paper so the batteries thereof must also become very thin, but the structures of lithium batteries that are currently in use are not suitable for or applicable to the very thin electronic devices.
Lithium thin-film batteries have been developed in order to solve the above-noted problem, but their charging performance per volume is worse than general lithium batteries, their production cost is three times as expensive, and they are congenitally dangerous because of the lithium. Therefore, it is difficult to apply them to bio-application fields such as artificial organs and micro-robots.
A supercapacitor that is quickly growing as a future energy storage means that will replace the lithium batteries is a next-generation energy storage device that can be quickly charged and discharged within several seconds, provides ten times higher power than rechargeable batteries, and provides a semi-permanent lifetime over 500,000 cycles. The energy storage of the supercapacitor per weight is substantially equivalent to 1/10 that of conventional batteries and the energy storage level thereof per volume is similar to that of the lithium batteries, and recent reports say that the supercapacitor outperforms the existing batteries regarding energy density and power density per volume.
The energy storage level per volume is more important for a very small electronic device that is light in weight than the weight so the film-type micro-supercapacitor as a power supply means that is very appropriate for the very small electronic device. Also, the film-type micro-supercapacitor includes no rare earth resources or heavy metals so it is inexpensive and environmentally friendly, and it generates no oxidation-reduction reaction so it is future energy storage means that is not explosive at all and is totally safe. The film-type micro-supercapacitor will replace existing batteries and be used in the field of very small electronic devices requiring a very small power supply such as accessory-style portable telephones that are thin like paper, micro-robots, artificial organs, smart cards, microelectromechanical systems (MEMS), and paper-like displays.
Discussions about techniques and scientific research on the film-type micro-supercapacitor have just begun, as with development of the lithium thin-film batteries.
An experimental result that is obtained by developing a ultrathin film type supercapacitor using graphene and that has proven that the supercapacitor can replace the batteries regarding its performance has been published in Nano Letters (Yoo et al., 2011, Vol. 11, pp. 1423-1427). Further, the collaborative research team of Toulouse University (France) and Drexel University (US) manufactured a supercapacitor electrode by using onion-like carbon (OLC) to evaluate remarkable improvements of energy and power characteristics and reported them to Nature Nanotechnology (Brunet et al., Vol. 5, pp. 651-654).
In this report, comparisons on the lithium battery, the electrolyte solution capacitor, and the conventional supercapacitor have shown excellent performance by showing that the OLC-based supercapacitor outperforms the conventional supercapacitor, its energy characteristic is almost equal to or better than the lithium battery, and its power consumption is equivalent to that of the electrolyte solution capacitor. Rapid growth of film-type supercapacitor related techniques is expected, according to the report.
The supercapacitor includes no lithium at all so it is estimated to be the best power supply in the aspect of safety acquisition. However, the existing supercapacitor has the same structure as the general battery so it is not easy to down-size it. In other words, the conventional supercapacitor has a stack structure in which two electrodes, a current collector, and a separation film are stacked in a sandwich form, so it is difficult to manufacture the conventional supercapacitor in a very small and thin shape to be used for the MEMS. Particularly, when graphene is used for the supercapacitor, the stack structure has a problem of ion mobility so it substantially deteriorates efficiency.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.